Multifunctional airway evaluator for orotracheal intubation

ABSTRACT

A multifunctional airway evaluator for orotracheal intubation includes first and second connected elongated arms, movable relative to each other about a pivot axis, a planar plate connected to the first arm and extending upwardly therefrom, and a gravity-operated angular indicator attached to the planar plate. The plate includes a distance scale on its front face, and the distance scale includes a plurality of spaced apart grade lines aligned radially with the pivotal axis and distance parameters associated with the grade lines, each of the distance parameters indicating a distance between the distal ends of the first and second arms when the arms are in a relative position. The gravity-operated angular indicator includes an axial pin disposed perpendicular to the planar plate, a rotating disk pivotally attached to and rotatable around the axial pin by gravity, and one or more angular measurement marker provided adjacent the rotating disk.

CROSS REFERENCE TO RELATED APPLICATION

This application is a continuation of patent application Ser. No.12/703,429, filed Feb. 10, 2010, now U.S. Pat. No. 7,954,251 B2, whichclaims the benefit under 35 USC 119(e) of provisional patent applicationSer. No. 61/202,297, filed Feb. 17, 2009. Both parent applications arehereby incorporated by reference in their entirety.

FIELD OF THE INVENTION

The present invention relates to a device for evaluating airway fororotracheal intubation, more particularly relates to a multifunctionalairway evaluator for orotracheal intubation and the method of use.

BACKGROUND OF THE INVENTION

Tracheal intubation is the placement of a flexible plastic tube into thetrachea to protect the patient's airway and provide a means ofmechanical ventilation. The most common tracheal intubation isorotracheal intubation where, with the assistance of a laryngoscope, anendrotracheal tube is passed through the mouth, larynx, and vocal cords,into the trachea. A bulb is then inflated near the distal tip of thetube to help secure it in place and protect the airway from blood,vomit, and secretions. Orotracheal intubation is often performed asneeded in medical procedures by anaesthesiologists and otherspecialists, such as intensivists, pulmonologists, and emergency roomdoctors.

Maintenance of airway patency is a primary responsibility ofanesthesiologists. Interruption of gas exchange, even for severalminutes, can result in catastrophic outcomes such as brain damage ordeath. It has been reported that the vast majority (85%) ofairway-related events involve brain damage or death, and as many as onethird of deaths attributable solely to anesthesia have been related toinability to maintain a patent airway. The difficulty of achieving apatent airway varies with anatomic and other individual patient factors,and identification of the patient with a difficult airway is vital inplanning anesthetic management so that orotracheal intubation andpositive pressure ventilation can be achieved safely. Several clinicalcriteria can be routinely assessed on patients prior to anesthesiaincluding mouth opening distance, Mallampati classification, neckmobility, ability to prognath, thyromental distance, body weight, andprevious history of difficult intubation.

Accurate preoperative prediction of potential difficulty with intubationcan help reduce the incidence of catastrophic complications by alertinganesthesia personnel to take additional precautions before beginninganesthesia and establishing an artificial airway. In addition, moreaccurate prediction of difficulty with intubation can potentially reducethe frequency of unnecessary maneuvers (for instance, awake intubation)related to false positive predictions.

Several evaluation criteria have been proposed. Recently, Janssens et alhave proposed a quantitative evaluation approach using airway difficultyscore (ADS) as shown in the table below. Airway Difficulty Scorerepresent the sum of the points for five criteria of difficultintubation. As shown, the total score can vary from 5 to 15, and ifscore is higher or equal to 8, ventilation and/or intubation areconsidered likely to be difficult.

Airway Difficulty Score (ADS) Score 1 2 3 Thyromental distance >6 cm 5-6cm <5 cm Mallampati class Class I Class II Class III & IV Mouth opening 4 cm 2-3 cm  1 cm Neck mobility Normal (≧35°) Reduced Fixed flexionUpper incisors Absent Normal Prominent If score ≧8, ventilation and/orintubation likely to be difficult (Janssens et al., European Journal ofAnaesthesiology, 2001, 18, 3-12)

In addition to the above five parameter, mandibular angle distance hasalso been considered important in evaluation of airway. Among thesetests, Mallampati class and upper incisors can be examined by visualobservation. However, determination of mouth opening distance,thyromental distance, mandibular angle distance, and neck mobility of apatient requires using measurement equipments.

Currently, limited tools are available for making the above describeddistance and angular measurements. Doctors use ruler, measuring tape,paquimeter, and also commonly use their fingers or hands, to make thedistance measurements. Moreover, there is no specific device availablefor clinical measurement of the neck mobility angle. This renders themeasurements difficult and less accurate, considering the subject of themeasurements and unnatural positions that the patient is in. Lack ofaccuracy in the measurements may result in life threateningconsequences, for example when a false negative is reported from themeasurements.

Furthermore, for distance and angular measurements at least twodifferent measuring devices are used. As such, doctors need to carry, orhave access to, more than one device for the required measurements. Onthe other hand, considering the subject and environment of themeasurements, the devices used should be either disposable or can besterilized if they are intended to be used repetitively. It is costly tosupply and maintain multiple disposable measurement devices.

Therefore, there exists a strong need for a measurement device that isdesignated and particularly suitable for providing accurate airwayevaluation for orotracheal intubation, and an integrated measurementdevice that can be used for both distance and angular measurements forairway evaluation. It is further desirable to have a low cost disposabledevice that can be conveniently carried by doctors or made readilyavailable in medical facilities.

SUMMARY OF THE INVENTION

In one aspect, the present invention is directed to a multifunctionalairway evaluator for orotracheal intubation. In one embodiment, themultifunctional airway evaluator comprises a first elongated arm havinga distal end and an opposing hinge end; a second elongated arm having adistal end and an opposing hinge end connected to the hinge end of thefirst arm by a pivot connection, the first and second arms movablerelative to each other about a pivotal axis of the pivot connection; aplanar plate connected to the first arm and extending upwardly from anupper edge of the first arm, between the hinge end and a middle portionof the first arm, and a gravity-operated angular indicator attached tothe planar plate. The plate includes a distance scale on a front face ofthe planar plate, and the distance scale includes a plurality of spacedapart grade lines, each thereof aligned radially with the pivotal axis,and distance parameters associated with the grade lines, each of thedistance parameters indicating a distance between the distal ends of thefirst and second arms when the arms are in a relative position. Thegravity-operated angular indicator includes an axial pin disposedperpendicular to the planar plate, a rotating disk pivotally attached toand rotatable around the axial pin by gravity, and one or more angularmeasurement marker affixed adjacent the rotating disk.

In one embodiment, the gravity-operated angular indicator furtherincludes a base fastened to the planar plate. The axial pin and therotating disk are attached to the base, and the angular measurementmarker is placed on a front surface of the base. The base has a shape ofa clip and is slid onto an upper portion of the planar plate.

In a further aspect, the present invention is directed to a method ofevaluation of airway for orotracheal intubation. The method comprisesproviding a multifunctional airway evaluator described above, placingthe distal ends of the first and second arms next to a first and asecond predetermined locations of the body of a patient, respectively,and recording a measured distance between the first and secondpredetermined locations from the distance scale; and affixing the planarplate at a third predetermined location of the body of the patient, witha vertical central axis of the rotating disk aligned with a zero-degreereference line of the gravity-operated angular indicator, and theninstructing the patient to carry out a flexion movement involvingtilting of the third location of the body, and recording an extent ofrotation of the rotating disk from the angular measurement marker of thegravity-operated angular indicator.

In one embodiment, the first and second predetermined locations of thebody are mandibular and maxillary central incisors, respectively, whilethe mouth of the patient is fully opened, and the measured distance ismouth opening distance of the patient. In another embodiment, the firstand second predetermined locations of the body are the thyroid notch andbone point of the mentum of the mandible of the patient, respectively,while the neck of the patient is in full extension, and the measureddistance is thyromental distance of the patient. In a furtherembodiment, the first and second predetermined locations of the body arethe left mandibular angle and the right mandibular angle of the patient,respectively, and the measured distance is mandibular angle distance ofthe patient.

In yet another embodiment the third predetermined location is thepre-auricular area of the patient, and the flexion movement is tiltingof the head of the patient upwardly to a maximum extent whilemaintaining cervical spine in a neutral position, and the extent ofrotation of the rotating disk represents neck mobility of the patient.

The advantages of the present invention will become apparent from thefollowing description taken in conjunction with the accompanyingdrawings showing exemplary embodiments of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a front view of the airway evaluator in one embodiment of thepresent invention, with the first and second arms in a horizontal andrelatively closed position.

FIG. 2 is a rear view of the airway evaluator at the position shown inFIG. 1, wherein the dotted line is merely provided to show the alignmentof the two arms with the pivotal axis.

FIG. 3 is a side view of the airway evaluator shown in FIG. 1.

FIG. 4 is an exploded view of the airway evaluator shown in FIG. 1. FIG.4A is a partial view of an alternative embodiment of the airwayevaluator shown in FIGS. 1 and 4, with the central axes of the two armsaligned with the pivot axis.

FIGS. 5A and 5B are front and rear views of the airway evaluator shownin FIG. 1, with the second arm rotated away from the first arm, as whenthe device is used for measurement.

FIG. 6 is a front view of a further embodiment of the airway evaluatorshown in FIG. 1, which includes threshold markers for evaluation ofairway.

FIG. 7 is a front view of the airway evaluator shown in FIG. 1, with theplanar plate tilted 35 degree from the horizontal position.

FIG. 8 is an illustrative view showing the mechanism of the distancescale of the airway evaluator.

FIG. 9 is an illustrative view showing the geometric relationship of thegravity-operated angular indicator.

FIG. 10 is a front view of the airway evaluator in a further embodimentof the present invention, in which the gravity-operated angularindicator is removable from the planar plate.

FIG. 11 is a side view of the airway evaluator shown in FIG. 10.

FIG. 12 is an exploded view of the gravity-operated angular indicatorshown in FIG. 10.

FIG. 13 is an illustrative view of a measurement of the mouth openingdistance of a patient using the airway evaluator shown in FIG. 10.

FIG. 14 is an illustrative view of a measurement of the thyromentaldistance of a patient using the airway evaluator shown in FIG. 10.

FIG. 15 is an illustrative view of a measurement of the mandibular angledistance of a patient using the airway evaluator shown in FIG. 10.

FIGS. 16A and 16B are illustrative views of a measurement of the neckmobility of a patient using the airway evaluator shown in FIG. 10.

It is noted that in the drawings like numerals refer to like components.

DETAILED DESCRIPTION OF THE INVENTION

In one aspect, the present invention provides a multifunctional airwayevaluator for orotracheal intubation.

Referring now to FIGS. 1-7, in one embodiment a multifunctional airwayevaluator 10 comprises a first elongated arm 20, a second elongated arm30, a planar plate 50 and a gravity-operated angular indicator 80.

As shown, the first elongated arm 20 has a distal end 22, an opposinghinge end 24, an inner edge 26 and an outer edge 28. The secondelongated arm 30 has a distal end 32, an opposing hinge end 34, an inneredge 36, and an outer edge 38, see FIGS. 1 and 5A. The hinge ends 24 and34 of first and second arms are connected together by a pivot connection40. The first and second arms are movable relative to each other about apivotal axis 42 of pivot connection 40. The pivot connection can beeffected by pivot pins, pivot screws or other suitable means. In theembodiment shown, hinge ends 24 and 34 of the two arms are connected bya headed pivot pin 44.

Preferably, the first and second arms are linear and have the samelength. The length of the first and second arms can be from about 9centimeter (cm) to about 18 cm, preferably from about 10 cm to about 14cm. Optionally, the two arms can be slightly tapered from their hingedends toward the distal ends. Preferably, hinge ends 24 and 34 of thefirst and second arms are enlarged, and inner edge 36 of second arm 30and inner edge 26 of first arm 20 are aligned with pivotal axis 42, asshown FIGS. 1-2 and 5-6. The advantages of such an alignment can bebetter understood in reference to the operating mechanism of the airwayevaluator and the method of use described in more detail hereinafter. Inthe embodiment shown, second arm 30 is disposed on a rear side of firstarm 20 behind planar plate 50. However, second arm 30 can also bedisposed on the front side of first arm 20, particularly when the secondarm is made of a transparent material, which will not obstruct thescales on plate 50.

Planar plate 50 is disposed between hinge end 24 and about the middleportion 25 of first arm 20, and extends upwardly from inner edge 26 offirst arm 20. Planar plate 50 is affixed to first arm 20. In theembodiment shown, planar plate 50 and first arm 20 are made of oneintegral piece of material, as such the first arm is stationary.However, planar plate 50 can also be a separate element, affixed tofirst arm 20 by fasten means such as adhesive, screws, or pins. Theplate and the first and second arms can be made of a thin plate solidmaterial, including but not limited to, postcard paper, three-ply paperor triplex paper, plastics, wood, and metal. Moreover, plate 50 can bemade of a same or different material from the material of the two arms.In one exemplary embodiment, the plate and both arms are made of atriplex paper having a thickness of 1 mm and a density of 28 g/m².

As shown in FIG. 1, plate 50 has an upper edge 52, a first side edge 54on the hinge end 24 of first arm 20, and an opposing second side edge 56about the middle portion 25 of first arm 20. Herein, middle portion 25of first arm 20 refers to a portion of the first arm from about onefourth to about three fourth of its length from the hinge end. In otherwords, the position of second side edge 56, or the width of plate 50 canvary substantially. In one exemplary embodiment, first and second arms20 and 30 have a length about 12.8 centimeter (cm), and the width ofplate 50, between first side edge 54 and the merging point of secondside edge 56 with the first arm, is about 7 cm. Preferably, second sideedge 56 is circularly curved relative to pivot axis 42. However, thesecond side edge can also have other shapes, for example, vertical ortapered.

As shown, plate 50 includes a distance scale 60 on front face 58 of theplate. Distance scale 60 includes a plurality of spaced apart gradelines 62 and distance parameters 64 associated with grade lines 62. Eachgrade line 62 is aligned radially with pivotal axis 42. Each distanceparameter indicates a corresponding distance between distal end 22 offirst arm 20 and distal end 32 of second arm 30, when the two arms arein a position relative to each other. Distance scale 60 is disposedcircularly relative to pivot axis 42. Preferably, distance scale 60 isdisposed along the circularly curved second side edge 56, which easesreading of the measured distance parameter associated with the gradeline with which the second arm 30 aligns. However, as can be appreciatedwhen plate 50 is made of a transparent material, the position of secondarm 30 relative to distance scale 60 can be clearly recognized withoutthe aid of circular side edge 56.

The distance parameters can be expressed by metric or English units,preferably by metric units, since subject measurements to be made by theairway evaluator are commonly expressed by metric units in medicalexaminations. Resolution of the distance scale 60 can be from 0.1 to 1cm, preferably about 0.5 cm.

In a further embodiment as shown in FIG. 6, optionally distance scale 60further includes one or more threshold markers, indicating one or morepredetermined threshold distances. As shown, threshold marker 66 aindicates a recommended threshold mouth opening distance, and thresholdmarker 66 b indicates a recommended threshold thyromental distance, andthreshold marker 66 c indicates a recommended threshold mandibular angledistance for orotracheal intubation. Moreover, threshold markers can befurther highlighted for easy recognition of clinically recommendedthresholds.

The operating mechanism of distance scale 60 can be understood inreference to FIG. 8. The geometrical relationship of the distancebetween first arm 20 and second arm 30 can be expressed by the followingequation:a ² =b ² +c ²−2ab·cos (β)where “a” is the distance between distal end 22 of first arm 20 anddistal end 32 of second arm 30, “b” is the length of first arm 20, “c”is the length of second arm 30, and β is the angle between the two arms.

As can be appreciated, the distance scale 60 depends on, or varies with,the length of the arms. In one exemplary embodiment, the length of thearms is about 11.6 cm from the distal ends to pivot axis 42. On theother hand, as can be further appreciated in FIG. 8, distance “a” ismeasured between the two lines that are in alignment with pivot axis 42.In the exemplary embodiment shown in FIG. 1 and also illustrated in FIG.8, the inner edge 26 of first arm 20 and the inner edge 36 of second arm30 are in alignment with pivot axis 42. As such, distance “a” asmeasured using airway evaluator 10 shown in FIG. 1 is the distancebetween the inner edges 26 and 36 of the first and second arms. As shownin FIG. 1, distance scale 60 starts from the inner edge 26 of first arm20, in other words, the zero point of distance scale 60 is in line withthe inner edge 26 of first arm 20. A measured distance is read at theposition with which the inner edge 36 of second arm 30 is aligned.However, it should be understood that other planes along thelongitudinal axis of the first and second arms can also be aligned withthe pivot axis of the device and the reading of a measurement can bemade at a corresponding position along the edge of the distal endaccordingly. For example, as illustrated as an alternative embodiment inFIG. 4A, if the pivot axis 42′ is in alignment with the central axes ofboth the first and the second arms 20′, 30′, instead of in alignmentwith the inner edge 26 and the inner edge 36 as shown in the embodimentshown in FIG. 1, then distance “a” between the two arms is the distancebetween the central axes of the two arms at their distal ends. With thisconfiguration, indicator lines along the central axes of the two arms,respectively, may be provided to assist the measurement.

Optionally, plate 50 may further include an angular scale 70 disposedaside distance scale 60. The angular scale 70 includes a plurality ofspaced apart grade lines 72 and angular parameters 74 associated withgrade lines 72. Each grade line 72 is aligned radially with pivotal axis42. Each angular parameter indicates an angle between first arm 20 andsecond arm 30. In the exemplary embodiment shown, grade lines 72 ofangular scale 70 are coincide with grade lines 62 of distance scale 60.However, grade lines 72 of angular scale 70 can be separate anddifferent from the positions of grade lines 62 of distance scale 60, forexample, when the angular parameters have a resolution larger or smallerthan that shown in the exemplary embodiment.

The gravity-operated angular indicator 80 is attached to planar plate50, preferably at an upper portion thereof. Gravity-operated angularindicator 80 includes an axial pin 82 disposed perpendicular to planarplate 50, a rotating disk 90 pivotally attached to and rotatable aroundaxial pin 82 by gravity, and one or more angular measurement markers 84affixed adjacent rotating disk 90.

Axial pin 82 can be made of metal or other suitable materials,preferably with a smooth exterior surface. Rotating disk 90 has anaperture 92, through which axial pin 82 is inserted (see FIG. 4).Aperture 92 has an inner diameter larger than the outer diameter ofaxial pin 82, as such disk 90 can rotate freely around the axial pin.Preferably, rotating disk 90 has a centered pointed upper end 94. Thepointed upper end 94 helps the reading of measured angles. In theembodiment shown, rotating disk 90 has a general tear drop shape with apointed upper end 94. However, other suitable shapes, such as anelongated triangle or rectangle, can also be used. Rotating disk 90 canbe made of plastics, metal or other suitable materials. It isadvantageous that the rotating disk is made of a transparent material,because angular measurement markers behind the rotating disk can beclearly visualized. Optionally, rotating disk 90 further includes apointer line 98 marked on the front surface of the disk downwardly frompointed upper end 94 along the vertical central axis of the rotatingdisk. Pointer line 98 helps reading of the measured angle, particularlywhen the rotating disk is transparent.

The mass center of rotating disk 90 is distanced from axial pin 82 orthe axis of rotation of the rotating disk. In the exemplary embodimentshown in FIG. 1, rotating disk 90 is attached to axial pin 82 at onethird of its length from the upper end 94, along vertical central axis91 of the rotating disk (see FIG. 9). The geometric relationship ofrotating disk 90 is further illustrated in FIG. 9. As shown, in aCartesian plane with the axis of rotation (A) as the origin and thevertical central axis 91 of the rotating disk aligned with x-axis, themass center (M) has a coordinate of x=−0.8 and y=0, the upper end 94 hasa coordinate of x=1 and y=0, and the lower end 96 of the disk has acoordinate of x=−2 and y=0. As can be appreciated, the rotationalmovement of rotating disk 90 is induced by gravity. When planar plate 50is tilted from a horizontal position as shown in FIG. 7, rotating disk90 rotates around axial pin 82 and always repositions its verticalcentral axis 91 to the vertical position.

As shown in FIGS. 1 and 4, angular measurement markers 84 are providedon front face 58 of planar plate 50 next to the upper portion ofrotating disk 90. The angular measurement markers can be provided byprinting, painting, or embossing. Angular measurement markers 84 includea zero-degree reference line 86, one or more assessment lines, 88 a, 88b, aligned radially with axial pin 82, and one or more angularparameters 89 associated with the assessment lines (see FIG. 4). Thezero-degree reference line and the assessment lines are stationary.Zero-degree reference line 86 is used to indicate a starting position ofa rotational movement of rotating disk 90. In the embodiment shown, azero-degree reference line 86 is also a vertical reference line. Sincerotating disk 90 is always in the vertical position, when thegravity-operated angular indicator 80 is in its vertical position,vertical central axis 91 of the rotating disk is in alignment with thezero-degree reference line 86, and the pointed upper end 94 of therotating disk points to zero-degree reference line 86. This typically isthe starting position of a measurement as further described hereinafterin reference to the method of use.

However, the zero-degree reference line may also assume other suitableorientations, for example as a horizontal reference line. With thisconfiguration, rotating disk further includes a horizontal indicatorline that is perpendicular to vertical central axis 91 of the disk shownin FIG. 9. In this case, when the stationary horizontal reference lineis in line with the horizontal indicator line on the rotating disk, itindicates a starting position of a rotational movement of the disk.

Assessment lines 88 a, 88 b represent at least one predeterminedthreshold angle that is numerically expressed by the angular parameter.In the embodiment shown, assessment lines 88 a, 88 b indicate a 35degree angle from the zero-degree reference line 86. Since assessmentlines 88 a, 88 b are aligned radially with axial pin 82 or axis ofrotation of rotating disk 90, the extent of rotation of rotating disk 90can be determined according to the assessment lines. The presence ofassessment lines 88 a and 88 b on both sides of the zero-degreereference line 86 provides flexibility in using the airway evaluator forangular measurement, as an angular measurement can be made in eitherdirection.

As can be understood, the operation of gravity-operated angularindicator 80 is induced by gravity, therefore, its operation isindependent of the operation of the arms of the airway evaluator.

FIGS. 10-12 illustrate a further embodiment of the multifunctionalairway evaluator of the present invention. As shown in FIG. 10,multifunctional airway evaluator 100 comprises a first elongated arm120, a second elongated arm 130, a planar plate 150 and agravity-operated angular indicator 180. The structures and operationmechanism of first and second arms 120 and 130 are the same as those ofthe first and second arms 20 and 30 of airway evaluator 10 describedabove. The structure of planar plate 150 is the same as that of plate 50of airway evaluator 10 described above, which includes the abovedescribed distance scale 60 and optionally angular scale 70 along asecond side edge 156.

Airway evaluator 100 includes a removable gravity-operated angularindicator 180 fastened on planar plate 150. As more clearly shown inFIG. 12, gravity-operated angular indicator 180 includes a base 170, anaxial pin 182 affixed perpendicularly to base 170, a rotating disk 190pivotally attached to and rotatable around axial pin 182 by gravity, andone or more angular measurement markers 184 affixed on base 170 adjacentthe upper portion of rotating disk 190.

As shown in FIGS. 11 and 12, base 170 has a shape of clip, with a frontpanel 172 and a rear portion 174. The distance between front panel 172and rear portion 174 is sufficient to tightly insert planar plate 150.Axial pin 182 and rotating disk 190 are disposed on the front side offront panel 172. Angular measurement markers 184 are printed on thefront surface of front panel 172. Base 170 is slid onto the upper edge152 of planar plate 150 and stays stationary as shown in FIG. 10. In oneexemplary embodiment, base 170 has a height about 2.6 cm and a widthabout 2 cm, and axial pin 182 is affixed about 1.3 cm from the top ofbase 170. Base 170 can be made of plastics, metals or other suitablematerials. In one exemplary embodiment, both base 170 and rotating disk190 are made of a transparent thermoplastic, for example syntheticpolymer of methyl methacrylate.

The structure of rotating disk 190 is the same as that of rotating disk90 described above. Similar to angular measurement markers 84 describedabove, angular measurement markers 184 include a zero-degree or verticalreference line 186, one or more assessment lines, 188 a, 188 b, alignedradially with axial pin 182, and one or more angular parameters 189associated with the assessment lines. Angular measurement markers 184are provided on the front surface of front panel 172, behind the upperportion of rotating disk 190. In the embodiment shown, zero-degreereference line 186 and assessment lines, 188 a, 188 b, radially extendfrom aperture 181 in which axial pin 182 is inserted. This clearly showsaxial pin 182 as the axis of rotation of rotating disk 190.

The operation mechanism of gravity-operated angular indicator 180 is thesame as that of the angular indicator 80 described above. It is notedthat in the embodiment shown in FIG. 10, base 170 is fastened on theupper edge 152 of planar plate 150, with rotating disk 190 disposed atthe front side of plate 150. However, when needed the direction of base170 can be reversed, namely with rotating disk 190 disposed at the rearside of plate 150. Moreover, base 170 may also be fastened on first sideedge 154. In this case, the zero-degree reference line and assessmentlines may be rotated 90 degrees from those shown in FIG. 10, andalternatively, when in use the airway evaluator can also be positioned90 degrees clockwise from that shown in FIG. 16A.

As can be appreciated, the airway evaluator of the present invention issmall in size, and it can be conveniently carried by the doctors intheir pockets. The airway evaluator can be either made as a disposabledevice for one time use, or made as a reusable device. As a disposabledevice, the planar plate is preferred to be made of postcard paper ortriplex paper. However, optionally the removable gravity-operatedangular indicator 180 of airway evaluator 100 may be a reusablecomponent, which can be detached from plate 150 and attached to a newplate 150. For multiple uses, the materials of all components of thedevice are suitable for sterilization.

In a further aspect, the present invention provides a method ofevaluation of airway for orotracheal intubation using themultifunctional airway evaluator described above. More specifically, themultifunctional airway evaluator of the present invention can be usedfor multiple distance and angular measurements involved in airwayevaluation. These include, but not limited to, measurements of mouthopening distance, thyromental distance, mandibular angle distance,mandibulo-hyoid distance, and neck mobility.

Mouth opening distance is defined as the distance between mandibular andmaxillary central incisors measured while a patient's mouth is fullyopened. However, there are three types of patients according to teethdistribution in the mouth, and the mouth opening distance is measuredaccording to the patient type. For a patient with complete dental arch,mouth opening distance is measured as the distance between the incisorsteeth. For a patient with incomplete teeth, mouth opening distance ismeasured as if they present complete dental arch. For a patient withoutteeth, mouth opening distance is measured as the distance between theupper and lower gingivae. It has been found that mouth opening distanceindicates movement of the temporomandibular joint and that significantlylimited mouth opening hinders exposure of the larynx. Typically, a mouthopening distance of 4 cm or more is considered normal. A thresholddistance of 4 cm for mouth opening distance can be indicated in thedistance scale 60 of airway evaluator 10 or 100, as illustrated in FIG.6.

Thyromental distance is defined as the distance between the bone pointof the mentum of the mandible and the thyroid notch while the patient'sneck is fully extended. This measurement helps in determining howreadily the laryngeal axis will fall in line with the pharyngeal axiswhen the atlanto-occipital joint is extended. Alignment of these twoaxes is difficult if the thyromental distance is <6 cm in adults, or <3finger breadths as traditionally stated; 6-6.5 cm is less difficult,while >6.5 cm is considered normal. A threshold distance of 6 cm forthyromental distance can be indicated in the distance scale 60 of airwayevaluator 10 or 100, as illustrated in FIG. 6.

Mandibular angle distance is defined as the distance between the leftand the right mandibular angles. Typically, a mandibular angle distanceof 9 cm or more is considered normal. A threshold distance of 9 cm formandibular angle distance can be indicated in the distance scale 60 ofairway evaluator 10 or 100, as illustrated in FIG. 6.

The neck or cervical spine mobility is determined by a flexion anglebetween two positions, namely from the first position when a patient'shead and cervical spine are in the vertical position, to the secondposition when the patient tilts his head upwardly to a maximum extent,while maintaining cervical spine in a neutral position. Typically, thisflexion angle equal or higher than 35 degree is considered normal.

FIG. 13 illustrates using multifunctional airway evaluator 100 describedabove to measure the mouth opening distance of a patient. The doctoradjusts the second arm 130 relative to first arm 120, and places distalends 122 and 132 of the first and second arms against or next to thepatient's mandibular and maxillary central incisors, respectively, whilethe patient's mouth is fully open. As shown, the inner edge 126 of firstarm 120 is placed in line with the upper edge of the mandibular centralincisors and the inner edge 136 of second arm 130 is placed in line withthe lower edge of maxillary central incisors. Then, the distance betweenthe inner edges 126 and 136 of the first and second arms at their distalends is read on the distance scale 60. As described above, using theembodiment of the device shown, the measured mouth opening distance isread on the distance scale 60 at the position that the inner edge 136 ofthe second arm is in line with. The measured mouth opening distance isrecorded in the patient's medical record.

FIG. 14 illustrates measurement of the thyromental distance of thepatient using multifunctional airway evaluator 100. Typically, thedoctor makes markers first at the patient's bone point of the mentum ofthe mandible and thyroid notch, respectively, according to conventionalmedical examination procedure. The doctor adjusts the second arm 130relative to first arm 120, and places distal ends 122 and 132 of thefirst and second arms against or next to the patient's thyroid notch andbone point of the mentum of the mandible, respectively, while the neckof said patient is in full extension. As shown, the inner edge 126 offirst arm 120 is placed in line with the marker of the thyroid notch andthe inner edge 136 of second arm 130 is placed in line with the markerof the bone point of the mentum of the mandible. Then, the distancebetween the distal ends of the first and second arms is read on thedistance scale 60 to obtain the measured thyromental distance, asdescribed above in detail in reference to mouth opening distancemeasurement. The measured thyromental distance is recorded in thepatient's medical record.

FIG. 15 further illustrates measurement of the mandibular angle distanceof the patient using multifunctional airway evaluator 100. As shown,distal ends 122 and 132 of the first and second arms are placed againstthe left mandibular angle and the right mandibular angle of the patient,respectively. Then, the distance between the distal ends of the firstand second arms is read on the distance scale 60 to obtain the measuredmandibular angle distance, as described above in detail in reference tomouth opening distance measurement. The measured mandibular angledistance is recorded in the patient's medical record.

FIGS. 16A and 16B illustrate the measurement of the neck mobility of thepatient using multifunctional airway evaluator 100. As shown in FIG.16A, planar plate 150 is first fixed at the pre-auricular area of thepatient, either by a double-sided tape, or by a finger pressing againstthe patient's face to hold plate 150 stationary. When plate 150 isfixed, the zero-degree reference line 186 of gravity-operated angularindicator 180 is positioned vertically. As shown, at this time thepointed upper end 194 of rotating disk 190 is aligned with zero-degreereference line 186. Then, the patient is instructed to lift up his chinto tilt his head upwardly to a maximum extent while maintaining thecervical spine in a neutral position.

As shown in FIG. 16B, when the patient's head tilts upwardly, the plate150 is tilted from its original position shown in FIG. 16A. However, atthe same time rotating disk 190 rotates around axial pin 182, and staysat the vertical position. Now, the pointed upper end 194 of rotatingdisk 190 points beyond assessment line 188 a. It is noted that usingairway evaluator 100, the neck mobility is judged by the extent ofrotation equal or higher than the predetermined threshold angle (beyondassessment line 188 a), or less than the predetermined threshold angle(within assessment line 188 a). In the example shown in FIG. 16B, thepatient's neck mobility is higher than the threshold angle of 35degrees. The extent of rotation, in other words the measured neckmobility, is recorded in the patient's medical record.

In FIGS. 16A and 16B, airway evaluator 100 is placed on the right sideof the patient's face. However, if for any reason it is not feasible toattach the device to the right side of the patient's face,gravity-operated angular indicator 180 can be detached, reversed, andfastened on plate 150 with the rotating disk 190 disposed on the rearside of plate 150. Then, plate 150 can be placed on the left side of thepatient's face to measure neck mobility as described above.

As can be appreciated, the multifunctional airway evaluator of thepresent invention has several advantages. The multifunctional airwayevaluator provides a measurement device that enables doctors or othermedical professionals to accurately evaluate airway for orotrachealintubation. This overcomes the difficulties involved in making therequired measurement without appropriate equipment, and reduces errorsintroduced by improper measurements. Accurate airway evaluation andpreoperative prediction of potential difficulty with intubation can helpreduce the incidence of catastrophic complications by alerting doctorsto take additional precautions before beginning anesthesia or otherprocedures.

As described above, all measured parameters are recorded in thepatient's medical record, which can be easily maintained in anelectronic medical record and made readily accessible to doctors. Theavailability of an objective, easily documented, reproducible airwayevaluation result in the medical record ultimately improves quality ofmedical care. For example, if the airway evaluation result in themedical record indicates a difficult intubation, a resident, fellow,certified registered nurse anesthetist, or junior doctor can request thepresence and/or assistance of a senior doctor during the procedure. Onthe other hand, if the evaluation result predicts a normal intubationwhile a difficult intubation occurs, the medical record will assist inany subsequent risk management or resolving medicolegal issues.

The airway evaluator of the present invention is an integratedmultifunctional device that integrates two different measurementmechanisms into one portable device. This allows all distance andangular measurements for airway evaluation for orotracheal intubation tobe performed using one single device. Moreover, the removable feature ofgravity-operated angular indicator 180 of airway evaluator 100 providesfurther flexibility of the device in clinical use. The multifunctionalairway evaluator is small and portable, and it can be convenientlycarried around by doctors in their pockets, or provided at variouslocations in hospitals or medical facilities where the subjectmeasurements may be performed. The multifunctional airway evaluator canbe manufactured with very low cost, and thus is particularly suitablefor mass production for a disposable device.

As can be appreciated, the utilities and advantages of themultifunctional airway evaluator of the present invention have met astrong need in airway evaluation and in improvement of the quality ofmedical care.

While the present invention has been described in detail and pictoriallyshown in the accompanying drawings, these should not be construed aslimitations on the scope of the present invention, but rather as anexemplification of preferred embodiments thereof. It will be apparent,however, that various modifications and changes can be made within thespirit and the scope of this invention as described in the abovespecification and defined in the appended claims and their legalequivalents.

What is claimed is:
 1. A multifunctional airway evaluator for orotracheal intubation comprising: (a) a first elongated arm having a distal end and an opposing hinge end; (b) a second elongated arm having a distal end and an opposing hinge end connected to said hinge end of said first arm by a pivot connection; said first and second arms movable relative to each other about a pivotal axis of said pivot connection; (c) a planar plate connected to said first arm, extending upwardly from said first arm between said hinge end and a middle portion of said first arm, said planar plate including a distance scale on a front face thereof, disposed along a side edge of said plate at said middle portion of said first arm, toward said distal ends of said arms; said distance scale including a plurality of spaced apart grade lines aligned radially with said pivotal axis and distance parameters associated therewith, wherein when said second arm is rotated to a position relative to said first arm for measurement, one of said grade lines of said distance scale aligned with said second arm indicates a measured distance between said distal ends of said first and second arms at said position; and (d) a gravity-operated angular indicator attached to said planar plate, said gravity-operated angular indicator including an axial pin disposed perpendicular to said planar plate, a rotating disk pivotally attached to and rotatable around said axial pin by gravity, and one or more angular measurement marker affixed adjacent said rotating disk.
 2. The airway evaluator of claim 1, wherein an inner edge of said second arm and an inner edge of said first arm are aligned with said pivotal axis, and said measured distance between said first and second arms at said position is a distance between said inner edges of said first and second arms at said distal ends thereof.
 3. The airway evaluator of claim 1, wherein said pivot axis is in alignment with central axes of said first and second arms, and said measured distance between said first and second arms at said position is a distance between said central axes of said first and second arms at said distal ends thereof.
 4. The airway evaluator of claim 1, wherein said first and second arms are linear and have a same length.
 5. The airway evaluator of claim 1, wherein said planar plate and said first arm are made of one integral piece of a material.
 6. The airway evaluator of claim 1, wherein said side edge of said planar plate at said middle portion of said first arm is circularly curved, and said distance scale is disposed along said circularly curved side edge.
 7. The airway evaluator of claim 1, wherein said distance parameters of said distance scale are in metric or English units.
 8. The airway evaluator of claim 1, wherein said distance scale further includes one or more threshold marker, indicating one or more predetermined threshold distance.
 9. The airway evaluator of claim 1, wherein said planar plate further includes an angular scale aside said distance scale.
 10. The airway evaluator of claim 1, wherein said rotating disk of said gravity-operated angular indicator has a mass center distanced from said axial pin.
 11. The airway evaluator of claim 10, wherein said rotating disk is attached to said axial pin at one third of a length of said rotating disk from an upper end thereof, along a vertical central axis of said rotating disk.
 12. The airway evaluator of claim 1, wherein a plane of said rotating disk is in parallel with said planar plate.
 13. The airway evaluator of claim 1, wherein said rotating disk has a pointed upper end.
 14. The airway evaluator of claim 1, wherein said angular measurement marker includes a zero-degree reference line adapted to indicate a starting position of a rotational movement of said rotating disk.
 15. The airway evaluator of claim 14, wherein said angular measurement marker of said gravity-operated angular indicator includes one or more assessment line aligned radially with said axial pin, representing at least one predetermined threshold angle, and one or more angular parameter associated with said threshold angle.
 16. The airway evaluator of claim 1, wherein said axial pin of said gravity-operated angular indicator is attached to said planar plate.
 17. The airway evaluator of claim 1, wherein said angular measurement marker of said gravity-operated angular indicator is provided on said front face of said planar plate.
 18. The airway evaluator of claim 1, wherein said gravity-operated angular indicator further includes a base fastened to said planar plate, said axial pin and said rotating disk are attached to said base, and said angular measurement marker is placed on a front surface of said base.
 19. The airway evaluator of claim 18, wherein said base has a shape of a clip and is slid onto an upper portion of said planar plate. 